1. Technical Field
The present invention relates to a stacked-layered thin film solar cell and a manufacturing method thereof. More particularly, the present invention relates to a stacked-layered thin film solar cell and a manufacturing method thereof wherein a connection groove and a third separation groove are configured inside a projection zone of a second separation groove so to prevent short-circuit faults.
2. Description of Related Art
Please refer to FIGS. 1A and 1B for a conventional stacked-layered thin film solar cell 1, which comprises a substrate 14, a first electrode layer 11, a semi-conductor layer 13, and a second electrode layer 12 in a series stacked structure. In a manufacturing process of such stacked-layered thin film solar cell 1, the substrate 14 is firstly deposited with the first electrode layer 11 and then receives a laser scribing treatment so as to form a plurality of unit cells 112 and first grooves 111. Then the first electrode layer 11 is deposited thereon with the semi-conductor layer 13, and the semi-conductor layer 13 is such laser scribed that each semi-conductor scribed groove 131 is distant from a said scribed groove of the first electrode layer 11 by about 100 microns. Afterward, the semi-conductor layer 13 is deposited thereon with a second electrode layer 12, and the second electrode layer 12 as well as the semi-conductor layer 13 are such laser scribed that each resultant scribed groove 121 is distant from a said semi-conductor scribed groove 131 by about 100 microns. By the foregoing deposited layers and laser scribing processes performed on each said layer, the stacked-layered thin film solar cell 1 composed of the unit cells 112 in serial is so established.
In a following packaging process, for eliminating problems about short-circuit faults and electric leakage, U.S. Pat. No. 6,300,556 proposes a method involving forming an isolation groove 15 by scribing the solar cell near a periphery thereof for partially removing the first electrode layer, the semi-conductor layer and the second electrode layer, and then mechanically removing the first electrode layer, the semi-conductor layer and the second electrode layer or films of the three layers outside the isolation groove 15 near a periphery of the substrate. Besides, the disclosure of U.S. Pat. No. 6,271,053 involves depositing the layers, dividing the deposited layers into serially connected solar cells, removing the second electrode layer and semi-conductor layer at peripheries of the unit cells so as to reveal the semi-conductor layer, and then thermally processing the revealed semi-conductor layer to oxidize its surface and thereby increase its resistance. Otherwise, US Patent Publication 2006/0,266,409 reveals the first electrode layer by removing the second electrode layer and the semi-conductor layer with a first laser before using a second laser to remove portions of the second electrode layer, the semi-conductor layer and the first electrode layer that have not been removed by the first laser.
In the above technology, for forming the isolation grooves, due to diverseness of the films, the first laser of a certain wavelength is used to remove the second electrode layer and the semi-conductor layer so as to form scribed grooves, and to repeatedly scribe the scribed isolation grooves to widen the same in order to enhance accurateness of a cutting process later performed on the first electrode layer. Afterward, the second laser of another wavelength is employed to cut the first electrode layer. Since the isolation grooves are formed by two types of laser beams of different wavelengths, the manufacturing procedures are complicated and therefore equipment costs as well as manufacturing cycle are enlarged. Furthermore, after the cutting process is performed, due to possible unevenness of the laser beams, part of the second electrode layer may be not fully removed and, in its melt state, remains on the first electrode layer, leading to short-circuit faults. Though using a single type of laser in length to process the three layers facilitates simplifying the manufacturing procedures, it is notable that the resultant thermal effect is greater and thus the induced short-circuit problem is more significant. Moreover, when thermal treatment is implemented at the late stage of the manufacturing procedures to oxidize the semi-conductor layer and thereby increase its resistance for averting the short-circuit problem, equipment costs and manufacturing cycle can be accordingly increased.
On the other hand, due to recombination of electrons and holes and loss of light, photoelectric conversion efficiency in a stacked-layered thin film solar cell is limited. Thus, an interlayer is usually arranged between a material of a higher energy level and another material of a lower energy level so that when light passes through the stacked-layered thin film solar cell, a portion of the light having short wavelengths that can be absorbed by the material of the higher energy level is reflected to extend a light path while a portion of the light having long wavelengths that can not be absorbed by the material of the higher energy level is led to the material of the lower energy level so as to improve light transmission. For example, U.S. Pat. No. 5,021,100 proposes a dielectric selective reflection film in a stacked-layered thin film solar cell. Since the interlayer, for connecting materials of different energy levels, possesses electric conductivity, electric leakage and short-circuit faults can easily happen during an edge isolating process of the interlayer. Therefore, U.S. Pat. No. 6,632,993 further provides cutting grooves 161 scribed on the interlayer 16 for eliminating electric leakage when a current passes through the interlayer 16, as shown in FIG. 1C. U.S. Pat. No. 6,870,088 also suggests a similar approach but further provides scribed grooves 181 on a photoelectric conversion layer between cutting grooves 171, as shown in FIG. 1D, so as to eliminate the above-mentioned problems. However, all of the above-mentioned conventional approaches were aimed to prevent short-circuit faults of the connection grooves and the interlayer but fail to address solutions to short-circuit faults of the scribe grooves that divide the entire solar cell into unit cells.